NEScaf Audio Filter

• SCAF audio filters are designed to limit how much of the audio spectrum will reach your earphones or speaker. In contrast, optional CW filters are narrow IF filters to limit how much of the RF spectrum your receiver responds to (rejecting unwanted signals above and below that narrow range). SCAF filters can actually be used with any receiver to effectively peak a desired audio frequency for improved CW reception.
• Some receivers are designed with excellent IF filters, yet still include an audio peak filter to enhance reception. Used together, the two filters allow clear single signal reception, and the technique is especially valuable if the desired signal is very weak. For example, when I am trying to copy SOTA signals from the mountains (usually 10 watts or less from small, portable antennas), I first tune my KX3 receiver to precisely zero beat the signal and then tighten the IF to 50 Hz to attenuate any adjacent interfering signals. Finally, I switch in the audio peak filter to enhance the single, wispy signal that I need to copy.

• An Audio filter is nice to have but when you are listening to CW with a wide SSB filter IF filter in the radio, you can get AGC "Pumping" that will Really knock down the level of the signal you are listening to , even when the audio filter is tuning out an interfering, strong signal
• Well, the nice thing about the TS-520 is that you can turn the AGC off to prevent pumping. With the AGC off, an audio filter works extremely well.
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